Perlite is an aggregate used in cement. Unlike sand, gravel or stone, perlite is not used for load-bearing concrete. Builders often use it for insulating and decorative concrete. Perlite is a volcanic mineral with a high R value, which means it does not conduct heat well; it is soft compared to load-bearing aggregates. Mixing perlite with concrete is a matter of proper portion; you must mix the correct ratio of perlite, cement and water. The more perlite in the mix, the higher the R value, but the lower the structural integrity of the cured concrete.
Pour a bag of cement into the 5-gallon bucket or mechanical mixer, depending on the size of job. Pour the appropriate amount of water, as determined by the cement manufacturer, into the container. Mix the two together with the plaster mixer or start the mechanical mixer to begin the process. Mix for several minutes until the concrete is uniformly saturated with water.
Add the air entraining agent, or AEA. Mix the correct ratio in respect to the purpose of your project. The manufacture provides ratios to determine the mix. The more AEA, the less download the concrete can sustain. However, AEA is important to prevent cracks and breaks in the concrete when it freezes and thaws. Mix the AEA into the cement until it is uniformly distributed.
Mix in the perlite. Like the AEA, the more perlite you add, the less structural stability the concrete assumes once cured. For less compressive strength, when the concrete will carry little to no load, eight cubic feet of perlite is appropriate. On the other hand, for a floor, two or three cubic feet is more appropriate. Mix the water, cement, AEA and perlite until the four components are equally distributed.